This disclosure relates generally to online systems, and more specifically to identifying accounts maintained by different online systems corresponding to a common user.
Online systems, such as social networking systems, allow users to connect to and communicate with other users of the online system. Users create profiles on an online system that are tied to their identities and include information about the users, such as interests and demographic information. The users may be individuals or entities such as corporations or charities. Because of the increasing popularity of online systems, and the significant amount of user-specific information maintained by online systems, an online system allows users to easily communicate information about themselves to other users and share content with other users. For example, an online photo and video sharing system generates content feeds for presenting photos and videos uploaded by its users to other users. In addition to photos and videos, other types of content uploaded and shared by online system users may be presented, such as stories describing actions performed by online system users, status updates, event announcements, activity invitations, location check-ins, or any other suitable information.
Multiple online systems may maintain information about a user describing the user to each online system and identifying actions performed by the user with each online system. Additionally, certain online systems may exchange information, such as information associated with users subject to privacy settings and other regulations, with each other. This allows an online system to leverage information maintained by another online system to improve content provided to a user or to provide additional functionality. However, different online systems typically associate different identifying information with a user, so an identifier associated with the user by an online system differs from an identifier associated with the user by another online system. An online system typically does not allow another online system to access certain information used by the online system to identify a user, use of different information identifying a user by different online systems may prevent an online system from obtaining information about the user from another online system with which the online system is authorized to exchange information.